1. Field of the Invention
The present invention relates to an internal combustion engine for mounting on a motorcycle and including a kick starting mechanism removably mounted relative to the engine for starting an engine by kicking. More particularly, the present invention is directed to a structure for blocking an oil supply hole of a kick idle bearing portion in the state where the kick starting mechanism is removed.
2. Description of Background Art
Various kinds of internal combustion engines of a type in which the kick starting mechanism is removably provided have been known, for example, Examined Japanese Utility Model Publication No. HEI 6-22143. One example is shown in FIG. 1.
The internal combustion engine 1 is of a one-cylinder/four-cycle type used for a motorcycle. A crank shaft 3 and a transmission 4 are contained in a crank case 2. The transmission 4 has a construction in which a gear group fitted to a main shaft 5 is meshed with a gear group fitted to a counter shaft 6. A clutch 7 is disposed at the end portion of the main shaft 5.
A crank gear 10 fitted to the crank shaft 3 at the end portion opposite from an AC generator 9 is meshed with a clutch gear 11 rotated integrally with a clutch outer 7a of a clutch 7, and a clutch center 7b is fitted to a main shaft 5.
The drive of the engine is transmitted from the crank shaft 3 to the main shaft 5 by way of the clutch 7. The drive force thus transmitted rotates the counter shaft 6 by way of the meshing of the gears of the transmission 4. The rotation of the counter-shaft 6 is transmitted to a rear wheel by way of a chain mounted around a sprocket 12 fitted to the end portion of the counter shaft 6.
The internal combustion engine 1 has a self starting mechanism. A self starting motor 20 is disposed over the crank shaft 3. A drive shaft 20a of the self starting motor 20 is meshed with one gear of integral gears 22, 23 rotatably supported by a supporting shaft 21. The other gear 23 is meshed with one gear 25 of gears 25, 26 formed integrally with a rotating shaft 24. The gear 26 is meshed with a large diameter gear 27 rotatably supported around the crank shaft 3 by way of a one-way clutch.
When the self starting motor 20 is driven, the drive torque is transmitted to the crank shaft 3 by way of the gears 22, 23, 25, 26, and 27, thus starting the engine.
The drive torque of the crank shaft 3 is not transmitted to the self starting motor 20 by the one-way clutch.
The internal combustion engine 1 can be provided with a kick starting mechanism, other than the above-described self starting mechanism. FIG. 1 shows the internal combustion engine including the kick starting mechanism.
The above-described clutch gear 11 is integrally fitted with an idle gear 13 rotatably supported by the main shaft 5, and the idle gear 13 is meshed with a kick idle gear 30 rotatably supported by the end portion of the counter shaft 6.
The kick idle gear 30 is prevented from being slipped-off by a plate 2a projecting within the crank case 2.
Under the counter shaft 6, a kick shaft 31 is rotatably supported by a bearing portion of an inner wall 2b provided in the crank case 2 and a bearing portion of a clutch cover 8.
The kick shaft 31 passes through a bearing portion 8a of the clutch cover 8 and projects from the exterior of the crank case 2. The base end of a kick arm 32 is fitted to the end portion of the kick shaft 31.
A dog clutch 33 is provided on the kick shaft 31. One dog clutch gear 33a, spline-fitted to the kick shaft 31, can be removably fitted to the opposed dog clutch gear 33b which is rotatably supported. The rotatably supported dog clutch gear 33b is meshed with the kick idle gear 30 rotatably supported by the counter shaft 6.
Accordingly, when the kick shaft 31 is rotated by operation of the kick arm 32, the dog clutch 33 is activated, and the kick starting torque is transmitted to the kick idle gear 30, idle gear 13, clutch gear 11, crank gear 10 and crank shaft 3 in this order. The torque can be thus transmitted to the crank shaft 3, not by way of the clutch 7, to start the engine.
An oil passage 6a is formed at a center shaft portion in the counter shaft 6, and which is radially branched to form a plurality of oil supply holes for supplying oil to specified bearing portions. An oil supply hole 6b is also formed in the bearing portion of the kick idle gear 30.
The above-described kick starting mechanism can be mounted when needed. In the state when the kick starting mechanism is not provided, the kick idle gear 30 is also removed. Thus, the oil supply hole 6a of the bearing portion is opened to the outside. The oil supply hole 6a must be blocked.
Conventionally, the oil supply hole 6a is blocked by a blocking structure shown in FIG. 6.
A cylindrical collar 01 having an inside diameter being substantially the same as the outside of the bearing portion of the counter shaft 6 is fitted to the bearing portion, to block an oil supply hole 6b, and a snap ring 02 is locked in a groove 03 formed at the end portion of the bearing portion for preventing the slip-off of the collar 01.
In the conventional way, to block the oil supply hole 6b, the two parts, namely the collar 01 and the snap ring 02, have been required. Further, it was also required to provide the groove 03 for locking the snap ring 02 to the counter shaft 6. This is disadvantageous in terms of manufacturing cost.